HEMT-compatible lateral rectifier structure

ABSTRACT

The present disclosure, in some embodiments, relates to a method of forming a transistor device. The method may be performed by forming an anode and a cathode over an electron supply layer disposed on a semiconductor material. A doped III-N semiconductor material is formed over the electron supply layer, and an insulating material is formed over the electron supply layer and the doped III-N semiconductor material. The insulating material continuously extends from over the anode to over the cathode. The insulating material is patterned to form sidewalls of the insulating material that define an opening over the doped III-N semiconductor material. A gate structure is formed directly between the sidewalls of the insulating material and over the doped III-N semiconductor material.

REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.15/959,459, filed on Apr. 23, 2018, which is a Continuation of U.S.application Ser. No. 14/583,391, filed on Dec. 26, 2014 (now U.S. Pat.No. 9,978,844, issued on May 22, 2018), which is a Continuation-in-Partof U.S. application Ser. No. 13/956,902, filed on Aug. 1, 2013 (now U.S.Pat. No. 9,806,158, issued on Oct. 31, 2017). The contents of theabove-referenced matters are hereby incorporated by reference in theirentirety.

BACKGROUND

A power semiconductor device is a semiconductor device used as a switchor rectifier in power electronics (e.g., power converters). Incomparison to low-power MOSFET devices, power semiconductor devices(e.g., power diodes, thyristors, power MOSFETs, etc.) are configured tohandle larger currents and to support larger reverse bias voltages.

Conventional power semiconductor devices are formed using silicon.However, in recent years the semiconductor industry has put significanteffort into developing gallium nitride (GaN) based power devices.Compared to conventional silicon-based power devices, GaN-based powerdevices feature characteristics such as lower on-resistance and theability to perform high-frequency operations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of some embodiments of ahigh-electron mobility transistor (HEMT) compatible lateral field effectrectifier (L-FER) device

FIG. 2 illustrates a graph showing performance parameters of someembodiments of a disclosed HEMT compatible gallium-nitride (GaN)rectifier device.

FIG. 3 illustrates a cross-sectional view of some embodiments of anintegrated chip comprising a disclosed L-FER integrated with anormally-off HEMT.

FIG. 4 illustrates a cross-sectional view of some embodiments of a HEMTcompatible L-FER device with a passivation layer.

FIG. 5 illustrates a cross-sectional view of some alternativeembodiments of a HEMT compatible L-FER device with a passivation layer.

FIG. 6 illustrates a flow diagram of some embodiments of a method offorming a HEMT compatible L-FER device.

FIGS. 7-13B illustrate cross-sectional views of some embodiments of anexample substrate upon which a method of forming a HEMT compatiblelateral field effect rectifier (L-FER) device is performed.

DETAILED DESCRIPTION

The description herein is made with reference to the drawings, whereinlike reference numerals are generally utilized to refer to like elementsthroughout, and wherein the various structures are not necessarily drawnto scale. In the following description, for purposes of explanation,numerous specific details are set forth in order to facilitateunderstanding. It may be evident, however, to one skilled in the art,that one or more aspects described herein may be practiced with a lesserdegree of these specific details. In other instances, known structuresand devices are shown in block diagram form to facilitate understanding.

In recent years, Gallium nitride (GaN) transistors have emerged as apromising alternative to silicon based transistors for many high powerapplications (e.g., power switches). GaN transistors, having aluminumgallium nitride/gallium nitride (AlGaN/GaN) heterostructures, offer anumber of performance advantages over conventional silicon devices. Forexample, GaN semiconductors may provide a lower on-resistance and higherswitching frequency than conventional silicon power devices.

Efforts have been made to provide for a two-terminal GaN power rectifierhaving good performance (e.g., a high reverse breakdown voltage, a lowforward turn-on voltage, and a low specific on-resistance) that iscompatible with a GaN HEMT (high electron mobility transistor). However,such efforts have largely failed. For example, the formation of Schottkybarrier diodes and p-i-n diodes on a doped bulk GaN present highbreakdown voltages and low-on resistance features, but the epitaxialstructures of Schottky barrier diodes and p-i-n diodes are notcompatible with the epitaxial structure of a GaN HEMT withoutsignificant performance loss (e.g., higher turn on voltages and onresistances). Alternatively, power rectifiers that are HEMT compatiblehave poor off leakage current, which is limited by Schottky contactreverse biasing leakage current.

Accordingly, the present disclosure relates to a high electron mobilitytransistor (HEMT)—compatible lateral field-effect rectifier device thatprovides for a high reverse breakdown voltage and low gate leakage. Insome embodiments, the rectifier device comprises an electron supplylayer located over a layer of semiconductor material at a positionbetween an anode terminal and a cathode terminal. A layer of doped III-Nsemiconductor material is disposed over the electron supply layer. Alayer of gate isolation material is located over the layer of dopedIII-N semiconductor material. A gate structure is disposed over gateisolation material, such that the gate structure is separated from theelectron supply layer by the layer of gate isolation material and thelayer of doped III-N semiconductor material. The layer of doped III-Nsemiconductor material modulates the threshold voltage of the rectifierdevice, while the layer of gate isolation material provides a barrierthat provides the rectifier device with a low leakage and high reversebreakdown voltage.

FIG. 1 illustrates a cross-sectional view of some embodiments of ahigh-electron mobility transistor (HEMT) compatible lateral field effectrectifier (L-FER) device 100.

The L-FER device 100 comprises a layer of semiconductor material 104disposed over a substrate 102 (e.g., a sapphire substrate, a siliconsubstrate, silicon carbide substrate, etc.). In some embodiments, thelayer of semiconductor material 104 may comprise a III-V semiconductormaterial or a III-nitride (III-N) semiconductor material. For example,in some embodiments wherein the L-FER device 100 comprises a galliumnitride rectifier device, the layer of semiconductor material 104 maycomprise a gallium nitride (GaN) layer (e.g., an unintentionally dopedGaN layer having a doping resulting from process contaminants).

An electron supply layer 106 is located over the layer of semiconductormaterial 104 at a position that extends between anode and cathodeterminals, 108 and 110, respectively comprising ohmic contact regionsdisposed over the layer of semiconductor material 104. The electronsupply layer 106 comprises a material having a band gap unequal to(e.g., larger than) that of the underlying layer of semiconductormaterial 104 so that a heterojunction, which serves as a channel regionof the HEMT compatible L-FER device 100, is located along an interfaceof the layer of semiconductor material 104 and electron supply layer106. During operation, the heterojunction causes the electron supplylayer 106 to supply charge carriers (e.g., electrons) to atwo-dimensional electron gas (2-DEG) 105 formed along the interface. The2-DEG 105 has high mobility electrons that are free to move between theanode terminal 108 and the cathode terminal 110. In some embodiments,the electron supply layer 106 comprises aluminum gallium nitride(AlGaN). In some embodiments, a thin film of AlGaN may be intentionallydoped to have a doping that provides carriers to the 2-DEG 105.

A layer of insulating material 112 may be disposed over the anodeterminal 108, the cathode terminal 110, and the electron supply layer106. In some embodiments, the layer of insulating material 112 maycomprise silicon nitride (Si₃N₄), for example. In some embodiments, thelayer of insulating material 112 may be on and in direct contact withthe anode terminal 108, the cathode terminal 110, and a portion of theelectron supply layer 106.

A layer of doped III-N semiconductor material 114 is positioned over theelectron supply layer 106. The layer of doped III-N semiconductormaterial 114 is laterally separated from the cathode terminal 110 by adrift length L_(D). The layer of doped III-N semiconductor material 114may comprise a p-type doping and/or an n-type doping in variousembodiments. In some embodiments, the layer of doped III-N semiconductormaterial 114 is laterally disposed between the layer of insulatingmaterial 112 and the anode terminal 108. The layer of doped III-Nsemiconductor material comprises gallium-nitride (GaN). In someembodiments, the GaN may comprise a bottom layer of GaN having a firstdoping type (e.g., a p-type doping) and a top layer of GaN, overlyingthe bottom layer of GaN, having a second doping type (e.g., an n-typedoping) different than the first doping type.

A layer of gate isolation material 116 is located over the layer ofdoped III-N semiconductor material 114. In some embodiments, the layerof gate isolation material 116 may comprise silicon dioxide (SiO₂),silicon nitride (Si₃N₄), gallium oxide (Ga₂O₃), aluminum oxide (Al₂O₃),scandium oxide (Sc₂O₃), hafnium oxide (HfO₂), or aluminum nitride (AlN),for example. In various embodiments, the layer of gate isolationmaterial 116 may have a thickness in a range of between approximately 5angstroms and approximately 30 angstroms. In some embodiments, a layerof isolation material 117 may also be located over the layer ofinsulating material 112. The layer of isolation material 117 may be thesame material as the layer of gate isolation material 116 and/or mayhave a same thickness as the layer of gate isolation material 116. Thelayer of gate isolation 116 suppresses gate leakage current, therebyimproving gate stability, providing the L-FER device 100 with a lowturn-on voltage, a low on-resistance, and a high breakdown reversevoltage.

A gate structure 118 is located over the gate isolation material 116 ata position overlying the layer of doped III-N semiconductor material114, such that the layer of gate isolation material 116 separates thegate structure 118 from the underlying doped III-N semiconductormaterial 114. In some embodiments, the gate structure 118 may comprise ametal gate structure. For example, the gate structure 118 may compriseone or more of titanium (Ti), nickel (Ni), aluminum (Al), nickelaluminum (NiAl), or tungsten (W), tungsten nitride (WN), or somecombination thereof, for example. In various embodiments, the gatestructure 118 may have a thickness (height) in a range of betweenapproximately 1,000 angstroms and approximately 5,000 angstroms.

A dielectric material 120 is disposed over the substrate at a positionoverlying the gate structure 118. The dielectric material 120 maycomprise a low-k inter-level dielectric (ILD) material such as silicondioxide (SiO₂), silicon carbide doped oxide (SiCO), etc. The dielectricmaterial 120 surrounds one or more metal interconnect layers 122configured to provide an electrical connection to the anode terminal108, the cathode terminal 110, and gate structure 118 of the L-FERdevice 100. In some embodiments, the one or more metal interconnectlayers 122 may comprise one or more metal vias 122 a configured toprovide a vertical connection and one or more metal wires 122 bconfigured to provide a lateral connection.

The one or more metal interconnect layers 122 are configured toelectrically couple the gate structure 118 to the anode terminal 108. Byconnecting the gate structure 118 to the anode terminal 108, the threeterminal device (the anode terminal 108, the cathode terminal 110 andthe gate structure 118) is converted to a two terminal lateral rectifierhaving a drift length L_(D), thereby allowing the forward turn-onvoltage of the L-FER device 100 to be determined by the thresholdvoltage of the channel (rather than the Schottky barrier of the anodeterminal 108). During operation, the one or more metal interconnectlayers 122 may be operated to bias the L-FER device 100 in a forwardbias mode of operation or in a reverse bias mode of operation. Forexample, applying a forward bias to the gate structure 118 causes thechannel to turn on, while applying a reverse bias to the gate structure118 causes the channel to turn off.

FIG. 2 illustrates a graph 200 showing performance parameters of someembodiments of a disclosed HEMT compatible gallium-nitride (GaN) lateralrectifier device. A first y-axis illustrates the on-resistance (i.e.,resistance drain to source) vs. the drift length L_(D) (x-axis). Asecond y-axis illustrates the breakdown voltage vs. the draft lengthL_(D) (x-axis).

As illustrated in graph 200, at a drift length L_(D) of 9 um, the GaNlateral rectifier device exhibits a reverse breakdown voltage of 660 Vand an on-resistance R_(on,sp) of 3.72 mOhm*cm². The resulting powerfigure of merit (BV²/R_(on,sp)) is 117 MW*cm⁻², which is comparable tostate-of-art GaN rectifiers that are not compatible with HEMT.

FIG. 3 illustrates a cross-sectional view of some embodiments of anintegrated chip 300 comprising a disclosed L-FER 302 integrated with anormally-off HEMT 304.

The L-FER 302 is described above in relation to FIG. 1. The normally offHEMT 304 comprises a source terminal 306, a drain terminal 308, and agate structure 310, disposed over a heterojunction (e.g., an AlGaN/GaNheterojunction). As shown, the L-FER 302 and the normally-off HEMT 304share a common epitaxial layer of semiconductor material 104 formed oversubstrate 102. In some embodiments, the L-FER 302 and the normally-offHEMT 304 may be manufactured as an integrated structure (e.g., on a sameintegrated chip) using a same fabrication process.

FIG. 4 illustrates a cross-sectional view of some embodiments of ahigh-electron mobility transistor (HEMT) compatible lateral field effectrectifier (L-FER) device 400 having a passivation layer 402.

HEMT compatible L-FER device 400 comprises a passivation layer 402disposed over the electron supply layer 106 and a doped III-Nsemiconductor material 114. In some embodiments, the passivation layer402 continuously extends from anode terminal 108 to cathode terminal110. In some embodiments, the passivation layer 402 abuts a top surfaceof the electron supply layer 106, a top surface of the doped III-Nsemiconductor material 114, and a sidewall of the doped III-Nsemiconductor material 114. In some embodiments, the passivation layer402 may also abut sidewalls of the anode terminal 108 and the cathodeterminal 110.

The passivation layer 402 is configured to passivate surface traps anddefects in the underlying electron supply layer 106 and doped III-Nsemiconductor material 114. By passivating surface traps and defects,the passivation layer 402 is able to increase device reliability and DCperformance. For example, typically during high-temperature reverse bias(HTRB) stress surface traps and defects are activated, causing currentdegradation in the HEMT compatible L-FER device 400. The passivationlayer 402 decreases current degradation caused by HTRB stress on theHEMT compatible L-FER device 400, so that the current before and afterHTRB stress is substantially the same (i.e., the passivation layer 402mitigates current degradation due to HTRB stress).

In some embodiments, the passivation layer 402 comprises a nitride basedpassivation layer. For example, in some embodiments, the passivationlayer 402 may comprise aluminum nitride (AlN) or silicon nitride(Si₃N₄). The passivation layer 402 may have a thickness t that is in arange of between approximately 5 angstroms and approximately 100angstroms, for example.

A layer of insulating material 112 is located over the passivation layer402. A gate isolation material 116 is arranged onto the layer ofinsulating material 112 and the passivation layer 402. A gate structure404 is disposed over the gate isolation material 116. In someembodiments, the gate structure 404 is disposed at a position that islaterally disposed between sections of the layer of insulating material112. In some embodiments, the gate structure 404 may have a sidewallthat is vertically aligned with a sidewall of the underlying gateisolation material 116 and that abuts the layer of insulating material112 and the gate isolation material 116. In such embodiments, thepassivation layer 402 may laterally extend past the gate structure 404.In some embodiments, the gate structure 404 is laterally separated fromthe anode terminal 108 by way of the layer of insulating material 112.

FIG. 5 illustrates a cross-sectional view of some embodiments of ahigh-electron mobility transistor (HEMT) compatible lateral field effectrectifier (L-FER) device 500.

HEMT compatible L-FER device 500 shows a doped III-N semiconductormaterial 502 having a height h that causes the doped III-N semiconductormaterial 502 to extend to a position that is vertically above the anodeterminal 108 to cathode terminal 110. It will be appreciated that theheight of the doped III-N semiconductor material 502 tunes the thresholdvoltage of the L-FER device. As shown in HEMT compatible L-FER device500, the height of the doped III-N semiconductor material 502 causes thepassivation layer 504 to abut opposing sidewalls of the doped III-Nsemiconductor material 502.

FIG. 6 illustrates a flow diagram of some embodiments of a method 600for forming a HEMT compatible lateral field effect rectifier (L-FER)device.

While disclosed method 600 is illustrated and described below as aseries of acts or events, it will be appreciated that the illustratedordering of such acts or events are not to be interpreted in a limitingsense. For example, some acts may occur in different orders and/orconcurrently with other acts or events apart from those illustratedand/or described herein. In addition, not all illustrated acts may berequired to implement one or more aspects or embodiments of thedescription herein. Further, one or more of the acts depicted herein maybe carried out in one or more separate acts and/or phases.

At 602, a substrate having an epitaxial heterojunction, between a layerof semiconductor material and an electron supply layer, is provided. Insome embodiments, the substrate comprises a layer of semiconductormaterial (e.g., a III-V semiconductor material) and an overlyingelectron supply layer, epitaxial grown over a substrate (e.g., asapphire substrate, a silicon substrate, silicon carbide substrate,etc.). The layer of semiconductor material and the electron supply layerhave different bandgaps, resulting in the formation of theheterojunction.

At 604, an anode terminal and a cathode terminal are formed at opposingends of the electron supply layer. The anode and cathode terminalscomprise ohmic contact regions.

At 606, a layer of doped III-N semiconductor material is selectivelyformed onto the electron supply layer. In some embodiments, the layer ofdoped III-N semiconductor material may comprise a doped gallium nitride(GaN) material having a p-type doping and/or an n-type doping.

At 608, a passivation layer may be formed over the doped III-Nsemiconductor material and the electron supply layer, in someembodiments. In some embodiments, the passivation layer may be formed onand in direct contact with the layer of doped III-N semiconductormaterial and the electron supply layer.

At 610, a layer of insulating material is selectively formed over thesubstrate at a position overlying the anode terminal, the cathodeterminal, the doped III-N semiconductor material, and/or the electronsupply layer. In some embodiments, the layer of insulating material maybe formed on and in direct contact with the passivation layer.

At 612, the layer of insulating material is selectively etched to exposethe doped III-N semiconductor material or the passivation layer.

At 614, a layer of gate isolation material is formed over the layer ofinsulating material, and the layer of doped III-N semiconductor materialor the passivation layer.

At 616, a gate structure is formed over the layer of gate isolationmaterial at a position overlying the layer of doped III-N semiconductormaterial.

At 618, one or more metal interconnect layers are formed within aninter-level dielectric (ILD) material to electrically couple the anodeterminal and the gate structure.

FIGS. 7-13 b illustrate some embodiments of cross-sectional views of asubstrate upon which a method forming a lateral field effect rectifier(L-FER) device, corresponding to method 600, is performed. AlthoughFIGS. 7-13 b are described in relation to method 600, it will beappreciated that the structures disclosed in FIGS. 7-13 b are notlimited to such a method, but instead may stand alone as a structure.

FIG. 7 illustrates a cross-sectional view 700 of some embodiments of asubstrate corresponding to acts 602-604.

As shown in cross-sectional view 700, a layer of semiconductor material104 and an electron supply layer 106 are epitaxially grown over asubstrate 102 (e.g., silicon, silicon carbide, sapphire, etc.). Thelayer of semiconductor material 104 and the electron supply layer 106have different bandgaps, thereby forming an epitaxial heterojunction. Insome embodiments, the layer of semiconductor material 104 comprises agallium-nitride (GaN) layer and the electron supply layer 106 comprisesan aluminum gallium nitride (AlGaN) layer.

An anode terminal 108 and a cathode terminal 110 are formed at opposingends of the electron supply layer 106. In some embodiments, the anodeterminal 108 and the cathode terminal 110 may be formed by depositing ametal (e.g., tungsten, aluminum, etc.) onto the underlying layer ofsemiconductor material 104 by way of a deposition technique (e.g.,chemical vapor deposition, physical vapor deposition, etc.) andselectively etching the deposited metal.

FIG. 8a illustrates a cross-sectional view 800 a of some embodiments ofa substrate corresponding to act 606.

As shown in cross-sectional view 800 a, a layer of doped III-Nsemiconductor material 114 (e.g., GaN) is selectively formed onto theelectron supply layer 106. In some embodiments, the layer of doped III-Nsemiconductor material 114 may comprise a layer of n/p gallium nitride(GaN). The layer of n/p GaN comprises a first layer of GaN 114 a havinga first doping type (e.g., an n-type doping) disposed onto the electronsupply layer 106, and a second layer of GaN 114 b having a second dopingtype (e.g., a p-type doping) disposed onto the first layer of GaN 114 a.For example, the layer of n/p GaN may comprise a bottom first layer ofGaN 114 a having a p-type doping and an overlying top second layer ofGaN 114 b having an n-type doping. The layer of doped III-Nsemiconductor material 114 may have a thickness and doping that can beselected to have a value that tunes the threshold voltage of the L-FERdevice.

FIG. 8b illustrates a cross-sectional view 800 b of some embodiments ofa substrate corresponding to acts 606-608.

As shown in cross-sectional view 800 b, a layer of doped III-Nsemiconductor material 114 (e.g., GaN) is selectively formed onto theelectron supply layer 106. A passivation layer 402 is formed onto thedoped III-N semiconductor material 114 and the electron supply layer106. In some embodiments, the passivation layer 402 is formed at aposition that abuts a top surface of the electron supply layer 106, atop surface of the doped III-N semiconductor material 114, and one ormore sidewalls of the doped III-N semiconductor material 114. In someembodiments, the passivation layer 402 may continuously extend fromanode terminal 108 to cathode terminal 110.

In various embodiments, the passivation layer 402 may be deposited byway of a deposition technique (e.g., atomic layer deposition (ALD),chemical vapor deposition (CVD), or physical vapor deposition (PVD),etc.) to a thickness that is in a range of between approximately 5angstroms and approximately 100 angstroms, for example. In someembodiments, the passivation layer 402 may comprise a nitride basedpassivation layer. For example, the passivation layer 402 may comprisealuminum nitride (AlN) or silicon nitride (Si₃N₄).

FIGS. 9a-9b illustrate cross-sectional views, 900 a and 900 b, of someembodiments of a substrate corresponding to act 610.

As shown in cross-sectional view 900 a, a layer of insulating material112 is formed at a position overlying the anode terminal 108, thecathode terminal 110, and the electron supply layer 106. In someembodiments, the layer of insulating material 112 may comprise siliconnitride (SiN) deposited by a vapor deposition technique.

As shown in cross-sectional view 900 b, the layer of insulating material112 is formed at a position that is on and in direct contact with theanode terminal 108, the cathode terminal 110, and the passivation layer402. In some embodiments, the passivation layer 402 and the layer ofinsulating material are different materials. For example, in someembodiments the passivation layer 402 may comprise SiN, while the layerof insulating material 112 may comprise AN.

FIGS. 10a-10b illustrate cross-sectional views, 1000 a and 1000 b, ofsome embodiments of a substrate corresponding to act 612.

As shown in cross-sectional view 1000 a, a masking layer 1002 is formedover the layer of insulating material 112. The masking layer 1002comprises an opening 1004 at a position overlying the doped III-Nsemiconductor material 114 (e.g., a position in which a gate structureis to be subsequently formed). In some embodiments, the layer ofinsulating material 112 is selectively exposed to an etchant 1006according to the masking layer 1002, to remove a portion of the layer ofinsulating material 112 and to thereby expose the underlying layer ofdoped III-N semiconductor material 114.

In some embodiments, the etchant 1006 may comprise a plasma etchant(e.g., an inductively coupled plasma reactive ion etchant in which highenergy ions etch away the layer of insulating material 112). Forexample, the etchant 1006 may be generated by a RIE plasma dry etchingprocess performed within a low pressure etching chamber.

As shown in cross-sectional view 1000 b, the layer of insulatingmaterial 112 is selectively exposed to an etchant 1006, according to themasking layer 1002, to remove a portion of the layer of insulatingmaterial 112 and to thereby expose the underlying passivation layer 402.

FIGS. 11a-11b illustrate cross-sectional views, 1100 a and 1100 b, ofsome embodiments of a substrate corresponding to act 614.

As shown in cross-sectional view 1100 a, a layer of gate isolationmaterial 1104 is formed over the layer of insulating material 112 andover the layer of doped III-N semiconductor material 114. In someembodiments, the layer of gate isolation material 1104 abuts the layerof doped III-N semiconductor material within an opening 1102 formed byselectively etching the insulating material 112 according to the maskinglayer 1002. The layer of gate isolation material 1104 provides a barrierbetween a subsequently formed gate structure (404) and the layer ofdoped III-N semiconductor material 114, thereby decreasing gate leakage.The layer of gate isolation material 1104 also prevents diffusion ofatoms from the subsequently formed gate structure (404) to theunderlying layer of doped III-N semiconductor material 114 during BEOLthermal processes used in formation of the one or more interconnectlayers.

The layer of gate isolation material 1104 may be deposited by way of avapor deposition process (e.g., ALD, CVD, PVD, etc.) to a thickness in arange of between approximately 5 angstroms and approximately 30angstroms. In some embodiments, the layer of gate isolation material1104 may comprise silicon dioxide (SiO₂), silicon nitride (Si₃N₄),gallium oxide (Ga₂O₃), aluminum oxide (Al₂O₃), Scandium oxide (Sc₂O₃),hafnium oxide (HfO₂), or aluminum nitride (AlN), for example.

As shown in cross-sectional view 1100 b, the layer of gate isolationmaterial 1104 is formed over the layer of insulating material 112 andover the passivation layer 402. In some embodiments, the layer of gateisolation material 1104 abuts the passivation layer 402 within anopening 1102 formed by selectively etching the insulating material 112according to the masking layer 1002.

FIGS. 12a-12b illustrate cross-sectional views, 1200 a and 1200 b, ofsome embodiments of a substrate corresponding to act 616.

As shown in cross-sectional views 1200 a and 1200 b, a gate structure118 is formed directly onto the layer of gate isolation material 1104.The gate structure 118 may be formed by depositing a metal (e.g., Ti,Ni, Al, NiAl, W, WN, etc.) using sputtering or physical vapordeposition, for example. The metal is then selectively etched to removea part of the metal and to define a gate structure 118.

FIGS. 13a-13b illustrate cross-sectional views, 1300 a and 1300 b, ofsome embodiments of a substrate corresponding to act 618.

As shown in cross-sectional views 1300 a and 1300 b, one or more metalinterconnect layers 122 are formed. The one or more metal interconnectlayers 122 are configured to short the anode terminal 108 to the gatestructure 118. By connecting the anode terminal 108 to the gatestructure, the three terminal device is converted to a two terminallateral rectifier.

In some embodiments, the one or more metal interconnect layers 122 maybe formed by depositing a dielectric material 120 over the substrate andselectively etching the dielectric material 120 to form one or moretrenches. The trenches are subsequently filled with a metal to form theone or more metal interconnect layers 122.

It will be appreciated that while reference is made throughout thisdocument to exemplary structures in discussing aspects of methodologiesdescribed herein (e.g., the structure presented in FIGS. 7-13 b, whilediscussing the methodology set forth in FIG. 6), that thosemethodologies are not to be limited by the corresponding structurespresented. Rather, the methodologies (and structures) are to beconsidered independent of one another and able to stand alone and bepracticed without regard to any of the particular aspects depicted inthe Figs. Additionally, layers described herein, can be formed in anysuitable manner, such as with spin on, sputtering, growth and/ordeposition techniques, etc.

Also, equivalent alterations and/or modifications may occur to thoseskilled in the art based upon a reading and/or understanding of thespecification and annexed drawings. The disclosure herein includes allsuch modifications and alterations and is generally not intended to belimited thereby. For example, although the figures provided herein, areillustrated and described to have a particular doping type, it will beappreciated that alternative doping types may be utilized as will beappreciated by one of ordinary skill in the art.

In addition, while a particular feature or aspect may have beendisclosed with respect to only one of several implementations, suchfeature or aspect may be combined with one or more other features and/oraspects of other implementations as may be desired. Furthermore, to theextent that the terms “includes”, “having”, “has”, “with”, and/orvariants thereof are used herein, such terms are intended to beinclusive in meaning—like “comprising.” Also, “exemplary” is merelymeant to mean an example, rather than the best. It is also to beappreciated that features, layers and/or elements depicted herein areillustrated with particular dimensions and/or orientations relative toone another for purposes of simplicity and ease of understanding, andthat the actual dimensions and/or orientations may differ substantiallyfrom that illustrated herein

The present disclosure relates to a high electron mobility transistor(HEMT)—compatible power lateral field-effect rectifier (L-FER) devicethat provides for a high-mobility and low gate leakage.

In some embodiments, the present disclosure relates to a high electronmobility transistor (HEMT)—compatible power lateral field-effectrectifier (L-FER) device. The L-FER device comprises a layer ofsemiconductor material disposed over a substrate, and an electron supplylayer disposed over the layer of semiconductor material at a positionbetween an anode terminal and a cathode terminal. A layer of doped III-N(III-nitride) semiconductor material is disposed over the electronsupply layer, and a passivation layer is disposed over the electronsupply layer and the layer of doped III-N semiconductor material. A gatestructure is disposed at a position vertically overlying the layer ofdoped III-N semiconductor material and the passivation layer.

In other embodiments, the present disclosure relates to a lateralfield-effect rectifier (L-FER) device. The L-FER device comprises alayer of semiconductor material disposed over a substrate, and anelectron supply layer disposed over the layer of semiconductor materialat a position laterally arranged between an anode terminal and a cathodeterminal. A layer of doped III-N (III-nitride) semiconductor material isdisposed over the electron supply layer, and a nitride based passivationlayer is disposed on and in direct contact with the layer of doped III-Nsemiconductor material and the electron supply layer. A layer of gateisolation material is disposed over the passivation layer at a positionoverlying the layer of doped III-N semiconductor material, and a gatestructure is disposed over the layer of gate isolation material.

In yet other embodiments, the present disclosure relates to a method offorming a lateral field effect rectifier (L-FER) device. The methodcomprises providing a substrate having an epitaxial heterojunctionbetween a layer of semiconductor material and an electron supply layer,and forming an anode terminal and a cathode terminal comprising ohmiccontact regions at opposing ends of the electron supply layer. Themethod further comprises selectively forming a layer of doped III-N(III-nitride) semiconductor material is onto electron supply layer. Themethod further comprises forming a passivation layer over the electronsupply layer and the doped III-N semiconductor material. The methodfurther comprises forming a gate structure at a position overlying thelayer of doped III-N semiconductor material.

The invention claimed is:
 1. A method of forming a transistor device,comprising: forming an anode and a cathode over an electron supply layerdisposed on a semiconductor material; forming a doped III-Nsemiconductor material over the electron supply layer, wherein the dopedIII-N semiconductor material is formed to have a first outermostsidewall that contacts a sidewall of the anode; forming an insulatingmaterial over the electron supply layer and the doped III-Nsemiconductor material, the insulating material laterally separating asecond outermost sidewall of the doped III-N semiconductor material fromthe cathode; patterning the insulating material to form sidewalls of theinsulating material that define an opening over the doped III-Nsemiconductor material; and forming a gate structure within the openingand over the doped III-N semiconductor material.
 2. The method of claim1, further comprising: forming a passivation layer to contact an uppersurface of the electron supply layer and to contact an upper surface andthe second outermost sidewall of the doped III-N semiconductor materialwherein the second outermost sidewall of the doped III-N semiconductormaterial is vertically between the upper surface of the doped III-Nsemiconductor material and the upper surface of the electron supplylayer and wherein the insulating material extends laterally past anoutermost sidewall of the passivation layer.
 3. The method of claim 2,further comprising: forming a gate isolation material onto thepassivation layer and the insulating material; and forming the gatestructure onto the gate isolation material.
 4. The method of claim 1,wherein the doped III-N semiconductor material laterally contacts theanode; and wherein the gate structure is separated from the anode by anon-zero space.
 5. The method of claim 1, further comprising: forming agate isolation material between the doped III-N semiconductor materialand the gate structure, wherein the gate isolation material continuouslyextends past one or more sidewalls of the gate structure.
 6. The methodof claim 1, further comprising: forming a gate isolation material withinthe opening after patterning the insulating material.
 7. The method ofclaim 1, further comprising: forming an inter-level dielectric (ILD)layer on both the insulating material and the gate structure and alongoutermost sidewalls of the insulating material.
 8. The method of claim1, further comprising: forming an ILD layer on the insulating material;and forming a conductive contact that extends through the ILD layer andthe insulating material to the anode.
 9. The method of claim 1, furthercomprising: forming a passivation layer onto the doped III-Nsemiconductor material and the electron supply layer, wherein thepassivation layer has a first outermost sidewall directly over the anodeand a second outermost sidewall contacting a sidewall of the cathode.10. The method of claim 1, wherein the doped III-N semiconductormaterial comprises an n-type dopant.
 11. A method of forming atransistor device, comprising: forming an anode and a cathode on anelectron supply layer disposed over an upper surface of a semiconductormaterial; forming a doped III-N semiconductor material over the electronsupply layer; forming an insulating material over the electron supplylayer and the doped III-N semiconductor material; etching through theinsulating material to form an opening over the doped III-Nsemiconductor material, wherein the insulating material has an outersidewall that vertically extends from the upper surface of thesemiconductor material to above the anode, the anode being disposedbetween the outer sidewall and the doped III-N semiconductor material;depositing a gate isolation material within the opening; and forming agate structure within the opening and over the doped III-N semiconductormaterial.
 12. The method of claim 11, further comprising: depositing thegate isolation material over the insulating material; depositing an ILDlayer over the gate isolation material; and forming a conductive contactthat extends through the insulating material, the gate isolationmaterial, and the ILD layer to the anode.
 13. The method of claim 11,wherein the gate isolation material has a lower surface that isvertically separated from an upper surface of the anode by theinsulating material along a direction that is perpendicular to the uppersurface of the semiconductor material.
 14. The method of claim 11,further comprising: a passivation layer disposed on the electron supplylayer and on an upper surface and a sidewall of the doped III-Nsemiconductor material, wherein the passivation layer has a firstoutermost sidewall separated from the upper surface of the semiconductormaterial by a first vertical distance and an opposing second outermostsidewall that is separated from the upper surface of the semiconductormaterial by a second vertical distance that is smaller than the firstvertical distance.
 15. A method of forming a transistor device,comprising: forming an electron supply layer on a semiconductormaterial; forming an anode and a cathode on the electron supply layer;forming a doped III-N semiconductor material on the electron supplylayer; forming a passivation layer on the electron supply layer and thedoped III-N semiconductor material; depositing a gate isolation materialon the passivation layer, wherein the gate isolation material laterallyextends past an outermost sidewall of the passivation layer; and forminga gate structure on the gate isolation material.
 16. The method of claim15, wherein the passivation layer has an uppermost surface that extendsto an outermost sidewall of the passivation layer.
 17. The method ofclaim 15, further comprising: forming an insulating material over thepassivation layer; patterning the insulating material to form an openingdirectly over the doped III-N semiconductor material, the openingexposing the passivation layer; depositing the gate isolation materialwithin the opening; and forming the gate structure within the opening.18. The method of claim 15, wherein the electron supply layer laterallyextends past an outermost sidewall of the passivation layer; and whereinthe semiconductor material laterally extends past an outermost sidewallof the electron supply layer.
 19. The method of claim 15, wherein thepassivation layer comprises a nitride based material.
 20. The method ofclaim 15, wherein the passivation layer is formed to continuously extendfrom a sidewall of the doped III-N semiconductor material to a top ofthe doped III-N semiconductor material.